I. Field of the Invention
This invention relates to multi-layer printed in which a plurality of unit substrates are laminated.
II. Description of the Background Art
Conventionally, heretofore known are coils using a plurality of sheet coils among coil parts using coils such as transformers and choke coils. For example, Japanese Patent Application Laid Open No. Hei-3-183106 in 1991 discloses the coil parts in which a plurality of printed substrates are formed thereon with circuit patterns being laminated.
Such conventional coil parts have finally been produced as completed independent electronics parts, therefore, the soldering is required for such coil parts to be mounted on upper surface of the printed substrate.
However, problems arise with regard to the printed substrate mounted with coil parts.
First, the independent coil parts formed separately in another way for the printed substrate are used, the whole printed substrate therefore comes thicker and larger in size together with the increased number of production processes for assembling including soldering.
Secondly, a circuit pattern of the printed substrate and coils of the coil parts include connections through terminal leads to provide an adverse effect of noise on using in a high-frequency circuit together with contact failure, thus disadvantage arises in view of reliability.
Third, the circuit patterns are printed on surface of the printed substrates, in addition, the circuit pattern is embraced on its two sides by the printed substrate, the resulted insufficient heat radiation of the circuit pattern introduces variation and deterioration with respect to its characteristics.